Coating apparatus including plural, sequential conveying means

ABSTRACT

Plural treating stations comprise two downwardly opening ovens facing respectively an upwardly opening fluidized bed coating tank and a quench tank. An endless conveyor means conveys the article to be treated into and out of the first oven and delivers same to a second endless conveyor means which conveys the article into and out of the fluidized coating tank. Third endless conveyor means transfers the article from said second to a fourth endless conveyor means which conveys same into and out of the second oven and the quench tank.

United States Patent [72] Inventor John W. Black 1,467,670 9/1923 Josephs, Jr. et a1. 266/4 Prairieville Township, Barry County, Mich. 1,876,050 9/1932 Fox 1 l8/423X [21] Appl. No. 625,123 2,048,938 7/1936 Larson et a1. 266/4BUX [22] Filed Mar. 22, 1967 2,341,766 2/ 1944 Fox 266/4 [45] Patented May 18, 19 2,368,130 l/l945 Fox 1 18/423 [73] Assignee Pemco Wheel Iompany 2,383,307 8/1945 Hansen 266/4 Kalamazoo, Mich- 2,413,987. 1/1947 Maxson 266/4 2,856,893 10/1958 Harris 118/57 3,262,420 7/ 1966 Bossi et a1. 118/423X 54 1 COATING APPARATUS INCLUDING PLURAL, Primary Emmi'1erM0rriS r SEQUENTIAL CONVEYING MEANS Attorney-Woodhams, Blanchard and Flynn 13 Claims, 14 Drawing Figs.

[52] US. Cl 118/6, Plural treating stations gmprise two 118/64, 118/69, 113/423, 266/4 downwardly opening ovens facing respectively an upwardly [51] 1131. C1 B05c 11/00 opening fluidized bed coating tank and a quench tank, An [50] Fleld 01 Search 1 18/ 423, endless conveyor means conveys the article to be treated into 1 and out of the first oven and delivers same to a second endless (Inqulred) conveyor means which conveys the article into and out of the 5 6 R f ed fluidized coating tank. Third endless conveyor means transfers 1 e erences the article from said second to a fourth endless conveyor UNITED STATES PATENTS means which conveys same into and out of the second oven 856,996 6/ 1907 Custer et a1 1 18/423X and the quench tank.

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INVENTOR. uo/m/ 14/. 544cm 4 Tram 5Y5 PATENTEU HAY I 8 1971 saw 07 0F 10 DEGPEASEP P\ NSE VAPN l SH (H20) 22 \8 23 m PPEHEA FLUlDlZE POST HEAT T D QUENCH OVEN BED OVEN INVENTOR. 4 Jay/v 01/. 5246/1 f PATENTEU Mm 197 SHEET 08 0F 10 INVENTOR. JOHN 14/ BLACK WW2 6M 7 A TWP/V5555 74W COATING APPARATUS INCLUDING PLURAL, SEQUENTIAL CONVEYING MEANS The fluidized bed process hasbeen used extensively for the purpose of coating articles with a plastic material, and the Gemmer US. Pat. No. 2,844,489 illustrates an existing apparatus by means of which the fluidized bed coating process can be utilized, However, this apparatus and the others which have been developed thus far have required a great deal of floor space in order to accommodate relatively large articles, and such apparatus has been unable to maintain a uniform heat in the articles to be coated without either creating ineff cient interruptions in the movement of the articles or an ex cessive amount of individual handling of the articles being coated. Moreover, particularly in the larger articles, the inefficiencies of the existing types of equipment have produced defective coatings necessitating careful and costly inspection of the coated articles.

One of the major deterrents to the successful use of completely automatic equipment for carrying out a fluidized bed coating process arises from the need for engaging the article while it is being coated, but without creating a defective coating. Clearly, the engagement of the article must be posi tive and secure, but this has heretofore necessitated the complete blocking of the engaged part or parts of the article from the coating process. Moreover, the structure of certain types of articles, for which coating is desired, is such that they cannot be readily engaged by hooks, clamps or the like which are attached to conveyor systems for this purpose.

Accordingly, the objects and purposes of this invention are to provide an apparatus for applying a coating to one or more articles, wherein:

l. The articles are presented to the apparatus which automatically engages the articles one at a time at uniform intervals and moves them along a predetermined path in a sequence of predetermined movements during which the articles are: (l) preheated; (2) immersed in a receptacle containing the coating material", (3) postheated to bake the coating material on the article; and (4) cooled as by dipping in a quenching liquid.

2. The articles are moved completely automatically from the time they are presented to the machine until they are quenched. 3. The preheating and postheating temperature are maintained substantially constant and the temperature of the articles in the preheating and postheating zones is maintained substantially uniform over the entire surface of the articles, in these respective zones in order to insure a uniform and highly acceptable coating upon the finished article. 4. The articles are equipped with fracturable hanger means which are engageable by the conveyor mechanism of the apparatus, but which can be separated from the articles following the coating process without disfiguring the appearance thereof. 5. The apparatus can be adapted to handle a continuous flow of relatively large articles while occupying a minimum of floor space, and the apparatus is arranged so that the articles can be presented to the apparatus and removed therefrom after the coating operation is performed by automatic equipment to minimize the manual engagement. 6. The apparatus, as aforesaid, can be operated at the relatively high temperatures desired for the production of a uniformly satisfactory coating without producing discomfort for the workman who tends the feeding and unloading of the machine.

Other objects and purposes of the invention will become apparent to persons familiar with the use and operation of article-coating equipment upon reading the following descriptive material and examining the accompanying drawings, in which:

FIG. I is a perspective view of a machine embodying the invention.

FIG. 2 is a rear end view of the machine.

FIG. 3 is a side elevational view of the machine, as indicated by the cutting line IIIIII in FIG. 2.

FIG. 4 is a sectional view taken along the line IV-IV in FIG. 2.

FIG. 4A is a perspective skeleton view of the frame.

FIG. 5 is a sectional view taken along the line V-V in FIG. 2.

' FIG. 6 is a perspective, broken line view illustrating the heat duct arrangement in the ovens of the machine.

FIG. 7 is an enlarged fragment of the conveyor system appearing in FIG. 5.

FIG. 8 is a sectional view taken along the line VIII-VIII in FIG. 4.

FIG. 9 is a sectional view taken along the line IXIX in FIG. 8.

FIG. I0 is an enlarged and detailed fragment of FIG. 5 incorporating an auxiliary article-handling device of the machine. I

FIG. 11 is a flow chart illustrating the process carried out by the machine.

FIG. 12 is an end view of the drive motors utilized in driving the conveyor system.

FIG. 13 is an electrical circuit capable of use in carrying out the invention.

FIG. 14 is an enlarged view of a fragment of the transfer mechanism in FIG. 4.

For convenience in reference, only, the terms upward," downward, forward," rearward, rightward" and leftward will designate corresponding directions as appearing in FIG. 3 and 4, the front" being on the left side thereof. The words inward" and outward" will refer to the geometric center of the device and designated parts thereof. Said terms will include derivatives thereof and words of similar importance.

The method for applying a plastic coating to a plurality of articles is illustrated by the flow chart appearing in FIG. 11. The articles, such as wire rod shelving 10, are first cleaned of all dirt and grease by dipping the articles into a degreasing tank 11, and then immersing them in a rinse tank 12 containing a solvent, such as water, to water, to wash the degreasing solution from the articles. The rinse tank may contain a detergent to aid in the removal of the degreasing solution. The articles are then removed from the rinse tank 12 and dipped in a varnish tank 13 wherein the articles are coated with a varnish. The articles are then removed from the varnish tank 13 and either stored or dried and then run through the apparatus described hereinbelow for applying a coat of plastic to the surface of the article. The foregoing steps can be performed manually, mechanically or by a combination of both.

The method, which may include the foregoing steps, comprises four further steps through which the article must pass in order to receive a coat of plastic which will be durable and will not be easily removable.

Specifically, the article is moved through a preheat oven 22 for a predetermined amount of time, which depends upon the size of the article to be coated. The temperature in the preheat oven is preferably in the range of 300 to 500 F., and is generally maintained at a temperature of approximately 350 F. The heated air within the preheat oven is circulated to prevent hot spots from developing within the oven. A standard wire rod shelf, for example, is held in the preheat oven 22 for a period of time ranging from to I50 seconds.

The article is transferred from the preheat oven 22 to a fluidized bed 18 which contains a quantity of powdered plastic, which is bonded to the article while it is held in the fluidized bed for a predetermined amount of time.

The article is removed from the fluidized bed 18 and is transported to a postheat oven 23. The temperature within the postheat oven is preferably in the range from 500 to 700 F., and is generally maintained at a temperature of approximately 600 F. The standard shelf 10, for example, is held in the postheat oven for a period of time ranging from 45 seconds to 50 seconds plus the travel time for moving the article into and out of the oven. The heated air is circulated to avoid hot spots. The amount of time which the article spends in each oven may, of course, be varied.

After the article has been in the postheat oven 23 for a tank 14 where it is cooled so that the operator can handle it.

DETAlLED DESCRlPTlON An apparatus for applying a coating, such as plastic, according to the method of the invention and as shown in FIG. 1 is generally referred to by the numeral 15. The apparatus or machine 15 is positioned on the floor 16 (FlG. 3) ofa building over a pit 17 which houses a fluidized bed 18 containing a powdered plastic and a quench tank 14 containing water. The machine further comprises an upright frame 21 which supports a pair of downwardly opening ovens 22 and 23 spaced upwardly from the fluidized bed 18 and the quench tank 14. The ovens are provided with heat ducts 173, 174, 186 and 196 (HO 6) for circulating the heated air throughout the ovens. The frame 21 (FIG. 4) further supports a conveyor system 26 which is equipped with an electrical system 27 (FIG. 13) for starting and stopping the various conveyors.

Having thus described the machine 15 in general terms, the component parts thereof will now be discussed more specifically.

FLUlDlZED BED The fluidized bed 18 FIGS. 3, 4 and 8) comprises a bin 31 having a bottom unit 32 supported on legs 33 which rest on the floor 34 of the pit 17. The bottom unit 32 has four sidewalls 36, 37, 38 and 39 and an integral bottom wall 41. A plurality of openings 42 (FlG, 8) are provided through the sidewalls 36, 37, 38 and 39, and are connected to a supply of air pressure indicated schematically by the letter S. Angle members 43, having flanges 46 and 47, are secured as by welding the flanges 47 to the inner surface of the walls 36, 37, 38 and 39. Likewise, angle members 48 having flanges 51 and 52 are secured as by welding to the flanges 52 to the outer surfaces of the walls 36, 37, 38 and 39 near the upper edges thereof.

The flanges 46 of the member 43 support a porous powder supporting wall 53 which includes a lower screen 54, a filter element 55 and an upper screen 56. The lower screen 54 includes a plurality of wire rods 57 and 58 secured as by welding transversely together to form a support for the filter element 55. The outer peripheral edges of the screen 54 is provided with a channel 59 having flanges 61 and 62 overlapping the edges of the upper and lower surfaces, respectively, of the screen 54.

The upper surface of the filter element 55 supports the screen 56 which has rods 63 and 64 transversely secured together as by welding. The outer peripheral edges of the screen 56 are provided with channels 66 having flanges 67 and 68 overlapping the upper and lower surfaces, respectively, of the screen 56. 1n this particular embodiment, the screen 56 does not extend across the full area defined by the walls 36, 37, 38 and 39, but is divided into two sections 69 and 70 to facilitate handling during removal thereof to replace the filter element 55. A rectangular frame 71 is positioned above the screen 56 and is secured to the flanges 46 of the members 43 by a plurality of bolts 72 extending through appropriately aligned openings in the frame 71, in the flanges 61 and 62, the filter element 55, and the flanges 67 and 68 of the bracket 66.

The bottom unit 32 (FIG. 8) supports an upper unit 76 having four sidewalls 77, 78, 79 and 80 which extend upwardly from the upper edges of the sidewalls 36, 37, 38 and 39, respectively. Angle members 82 having flanges 83 and 84 are secured as by welding along the flange 83 to the outer surface of the walls 77, 78, 79 and 80 near the lower edges thereof. A seal 86 is provided between the flanges 51 of the members 48 and the flanges 84 of the member 82. A plurality of bolts through appropriately aligned openings in the flanges 51 and 84 compress the seal 86 therebetween and secure the upper unit 76 to the bottom unit 32. A pair of openings 108 are provided in the wall 79 above the member 82.

A plurality of pins 88 (HO. 9) extend inwardly from the walls 78 and 80 of the upper unit 76. The pins 88 support a screen 89 which has a plurality of rods 91 and 92 transversely secured together as by welding. Channels 93 having flanges 94 and 95 overlap the edges of the upper and lower surfaces,

respectively, of the screen 89. A plurality of springs 96 are provided along the sides of the screen 89 and are fastened at one end to the upper surfaces of the channels 93 and extend to and are fastened at the other ends to brackets 97 secured to the inner surfaces of the walls 77, 78, 79 and 80, above the plane of the screen 89.

1n this particular embodiment, the left end (FIG. 8) of the screen 89 is provided with two pairs of springs 98 and 99. The springs 98 extend upwardly from the screen 89 and are secured to the brackets 97 on the wall 77 in about the same manner as the springs 96. However, the springs 99 extend horizontally away from the left edge of the screen 89 to a bracket 101 secured to the wall 77. The purpose of this construction will become apparent later in the discussion. Springs 102 extend between and are secured to the right end of screen 89 and brackets 103 secured to the inner surface of the wall 79.

A pair of brackets 104 (FlGS. 8 and 9) are secured to the upper surface of the frame member 93 along the right edge thereof. A pair of shafts 105, which are pivotally secured by pins 106 to the brackets 104, extend through bellows 107 which are secured to the wall 79 and seal the openings 108 therethrough. The outer ends of the shafts 105 are connected to eccentrics 109 driven by a motor 111, secured to the outer surface of the wall 79. The upper edge of the walls 77, 78, 79 and 80 are provided with outwardly'extending flanges 112 (FIG. 4).

QUENCH TANK The quench tank 14 (FIG. 4), which has a bottom wall 114 and four sidewalls 115, 116, 117 and 118, holds a quantity of water 119. The upper part of the wall 115 is provided with an overflow opening 121 which is connected to a drain pipe (not shown) to remove the water 119 from the tank 14 at a slow rate. The bottom portion of the wall 117 (FIG. 3) is provided with an opening 122 connected to an inlet pipe 123 which is connected to a source P of water under pressure such as a reservoir and pump. The purpose of this construction will become apparent later in the discussion.

In this embodiment, the quench tank 14 is positioned in I front of the powder bin 31 as illustrated in FIG. 3. The powder bin 31 and the quench tank 14 are aligned with the various parts of the conveyor system 26 as will be explained hereinafter.

FRAME STRUCTURE The frame structure 21 is generally similar on opposite sides of the centerline of the machine. Thus, one side (the left side in FIG. 1) will be described in detail, and the suffix A will be used with the same numerals in referring to corresponding parts of the machine on the other side (right side, P10. 1) of the machine.

The frame 21 (FIG. 1) consists of a pair of parallel channel beams 126and 126A which rest on the floor 16 of the building and extend across or adjacent the mouth of the pit 17. A pair of l-beams 128 and 129 (FIG. 4) extend between and are secured to the channel beams 126 and 126A. The lower ends of the vertical corner beams 131, 132, 133 and 134, as well as the side beam 136 between the beams 131 and 132, are supported upon and secured to the channel beams 126 and 126A. Midway (FIGS. 1, and 4A) between the upper and lower ends of the beam 136, a beam 137 is secured to and extends rearwardly from the beam 136. The spaced beams 138 and 139 extend upwardly from the beam 137, and they are parallel with and spaced from the beam 136 in a manner which will be hereinafter described.

Brackets and 135A (FlGS. 4 and 5) are secured to the beams 132 and 133, respectively, and extend rearwardly therefrom. The bracket 135, for example, has a pair of U- shaped article support recesses 140 and to receive the articles as will become apparent later in the discussion.

A pair of parallel, spaced beams 141 and 142 extend up- -wardly from and are secured to the beam 126 between the A beam 143 (FIG. 1) is secured to and extends between the upper extensions of the beams 131 and 134. Likewise. a beam 144 (FIG. 2) is secured to and extends between the upper ends of the beams 132 and 133. A beam 148 (FIG. 4) extendsbetween and is secured to the upper ends of the beams 131 and 132. A beam 149 (FIG. 5) extends between and is secured to the upper ends of the beams I33 and 134. A beam 146 (FIG. 3) extends parallel to the beams 143 and 444 between the upper ends of the beams 136 and 136A and is secured thereto as well as to the beams 148 and 149. A beam 147 extends parallel to the beam 146 between the upper ends of the rails 141, 142, and 141A, 142A and is secured thereto as well as to the beams 148 and 149. A beam 152 is secured at its ends to the beams 148 and 149. A beam 151 extends between the beams 132 and 136 and is secured thereto along the upper surface of the beam 126. Likewise, a beam 151A extends between the beams 133 and 136A and is secured thereto along the upper surface of the beam 126A.

A diagonal support channel 153 (FIG. 2) is secured at its lower end to the inner surface of the beam 126 and at its upper end to the upper ends of the intermediate posts 155. Likewise, a support channel 154 is secured at its lower end to the inner surface of the beam 126A and at its upper end to the upper end of the post 155 near the upper end of the support channel 153.

The beams 143, 144, 146, 147, 148, and 149 define a horizontal platform 156, the purpose of which will be discussed hereinbelow.

A wall 157 is secured to the beams 131 and 136 and extends from the beam 126 to the beam 148. The wall 157 is provided with window 158. Likewise, a wall 159 is secured to the beams 134 and 136A and extends from the beam 126A to the beam 149.

A supplemental frame structure 236 is supported on the frame structure 21, as illustrated in FIG. 1, and .has similar parts on both sides of the machine 15. Thus, one side, only, will be described. The supplemental frame 236 comprises a pair of vertical and parallel beams 237 and 238 secured to and extending upwardly from the beam 148. A horizontal beam 239 is secured to and extends between the upper ends of beams 237 and 238. A bearing 241 is secured upon the beam v 239 between the ends thereof. A pair of parallel and vertically spaced beams 242 and 243 are secured at their ends to the beams 237 and 238. Bearings 244 and 246 are secured upon the beams 242 and 243, respectively, between the ends thereof. A horizontal beam 247 extends frontwardly from the beam 238 and is secured thereto near its upper end. The beam 247 is braced by a pair of beams 249 and 251. A bearing 248 is secured upon the beam 247 between the ends thereof.

OVEN STRUCTURE The platform 156 and supplemental frame 236 (FIG. 1) support an oven structure 161 comprising a preheat section 22 (FIG. 4) and apostheat section 23. More particularly, the oven structure 161 comprises four vertical sidewalls I62, 163, 164 and 165 connected at their upper ends to a top wall 166. An intermediate wall 167 is disposed between and parallel with the walls 162 and 164. All of the said walls of the oven are insulated to retain the heat within the oven and maintain uniform temperatures. The intermediate wall 167 divides the oven structure 161 into two ovens, namely, the preheat oven 22 defined by the walls 163, 164, 165 and 167, and the postheat oven 23 defined by the walls 162, 163, 165 and 167.

The beam 147 supports a platfonn 168 (FIG. 4) which is rigidificd by a plurality of braces 169. The rear edge of the platform 168 and the lower edge of the wall 164 define an opening 171. The front edge of the platfonn 168 and the lower edge of the wall 167 define a second opening 172. The platform 168 supports a heat duct 173 which extends between the sidewalls and 163 in the preheat section 22. The top wall 166 supports within the preheat oven 22 a heat duct 174 which extends between the sidewall 165 and the sidewall 163 and is provided with a plurality of openings 183 (FIG. 6) in the lower wall 184 thereof.

The heat duct 173 (FIG. 6) is provided with a pair of slots 176 and 177 in the sidewalls 178 and 179, respectively. The slots 176 and 177 are provided with gates 181. and 182, respectively, which are movable vertically to provide a means of adjustment for the width of the slots 176 and 177.

The beam 152 supports a heat duct 186 (FIG. 6) having a pair of slots 187 and 188 in the sidewall 191 and 192, respectively. A pair of gates 193 and 194 are secured to the sidewall 191 and 192 and are movable vertically to provide a means of adjustment for the width of the slots 187 and 188.

The top wall 166 (FIG. 4) supports within the postheat section 23 the heat duct 196, which has a plurality of openings 197 in the bottom wall 198 thereof. The end of the duct 196 is closed adjacent the wall 165.

The corresponding ends of the heat ducts 174 and 196 pass through the wall 163 and are interconnected by a duct 199 (FIGS. 1 and 6). Likewise, the heat ducts 173 and 186 pass through the wall 163 and are interconnected by a duct 201. The duct 201 has a damper 209 to regulate the passage of the heated air therethrough.

Corresponding ends of the ducts 173 and 174 pass through the wall 165 and are connected through a heating unit 202 ofia conventional type, and a fan unit 203 which may be of the centrifugal type. More particularly, one end of the duct 204 is connected to the end of the heat duct 174 which extends through the wall 165, and the other end of duct 204 is connected to the upper end of the heating unit 202, which may be of the gas burning type. The lower end of the heating unit 202 is connected to the input of the fan unit 203, the output'of which is connected to the end of the heat duct 173 extending through the wall 165.

A fresh air intake (FIG. 3), which is connected to the heating unit 202, includes air moving and filtering devices of a conventional type (not shown) for supplying air to the heating unit 202.

The duct 186 and the lower edge of the wall 167 (FIG. 4) define an opening 211, and the duct 186 and the lower edge of the wall 162 define an opening 212.

HOOD STRUCTURE The front flange 112 (FIG. 4) of the powder bin 31 supports a panel 213, which extends upwardly and is secured along its upper edge to a rail 214 which extends between the plate walls 157 and 159 and is secured to ribs 216 and 216A, respectively, thereon. The end edges of the panel 213, which extends along the flange112, are spaced from the plate walls 157 and 159 to permit the passage of the conveyor chains therebetween, as will be discussed hereinafter.

A trough 218, which is secured to the upper portion of the panel 213, and to the upper portion of the quench tank 14, extends therebetween. A bar 220 (FIG. 10) is secured at one end to the wall 116, adjacent the upper end of quench tank 14, and at the other end to a point on the wall 118 spaced below the upper edge thereof.

The rear flange 112 (FIG. 4) supports a channel-shaped panel member 219, to which a shield 221 is secured. Said shield 221 has a vertical portion which extends upwardly to a position aligned with the upper surface of the beam 151, and a substantially horizontal portion 222 which slopes upwardly and rearwardly away from the upper edge of the vertical portion. A downwardly sloping flange 223 extends downwardly and rearwardly from the rear edge of portion 22 just above the shaft 293.

A vertical panel 224 (FIG. 4) is secured along the lower edge thereof to the rear edge of the flange 223 of the shield 221. A horizontal panel 226 is secured to the upper edge of the panel 224 and extends frontwardly (FIG. 4) away therefrom. An end wall 227 is secured to the left edges of the panels 224 and 226, and a wall 228 (FIG. 1) is securcdto the rightward edges of the panels 224 and 226. The wall 227 is parallel to and spaced from the beams 136, 137, 138 and 139, and the wall 228 is parallel to and spaced from the beams 136A, 137A, 138A and 139A. The walls 224, 226, 227, and 228, as well as the portions 222 and 223 of shield 221, define a hood 231. The front edges of the panels 226, 227, and 228 and 222 define an opening 229 into the hood 231.

The panel 224 is provided with plurality of openings 232 (FIG. 4), and a conduit 233 is secured to the rear side of the panel 224 so that it communicates with the openings 232. The rear end of the conduit 233 is secured to the wall 234 of an exhaust duct 236 which has a set of openings 236 into said conduit 233. The exhaust duct 236 is secured to and between the rails 141, 142. 141A and 142A. and extends the full width of the machine 15.

CONVEYOR SYSTEMS The conveyor system 26 is substantially symmetrical on opposite sides of the center line of the machine extending from the front to the rear thereof. Therefore, only one side of the conveyor system will be described, namely the left side illustrated in FIG. 4. The other side of the system, illustrated in FIGS. 3 and 5, will have corresponding reference numerals with the suffix A added thereto to denote the identical parts. The left side of the conveyor system 26 comprises four conveyors 252, 253, 254 and 255. The conveyor 252 comprises an endless chain 257 supported upon sprockets 258, 259, 260 and 261. The sprockets 258 and 259 are supported on shafts 262 and 263, respectively, which are rotatably supported by the bearings 241 and 246, respectively, on the outer side of the wall 163 of the oven structure 161. The sprocket 261 is supported upon a shaft 264 which is rotatably supported by a bearing 266 (FIG. 1) secured to the beam 132. The sprocket 260 is supported upon a drive shaft 267 which is rotatably sup ported by a bearing 268 mounted upon the beams 141 and 142. The other end of shaft 267 is supported by a bearing 268A secured to the rails 141A and 142A (FIG. 3). The shaft 267 further supports a sprocket 271 adjacent the outer side of the bearing 268A.

A plurality of article-engaging hooks 272 are pivotally connected to and between the chains 257 and 257A. In this particular embodiment, the conveyor 252 supports six such article-support hooks. The forward reach of the conveyor 252 *passes between the sidewall of the preheat oven and the platform 168 supporting the duct 173. Similar clearances are provided in connection with the other conveyor chains discussed herein.

The second conveyor 253 (FIG. 4) comprises an endless chain 273 supported upon a pair of vertically spaced sprockets 274 and 276. The sprocket 274 is supported upon a shaft 277 which is rotatably supported by the bearing 244 disposed along the outer surface of the wall 163 of the oven structure 161. The sprocket 276 is supported upon a drive shaft 278 which is supported at both ends by bearings (not shown) secured to the beams 138, 139 and 138A, 139A. The end of the shaft 278 (FIG. 3) supports an additional sprocket 279. The shaft 278 extends between the vertical beams 138A and 139A so that the sprockets 276A and 279 are on opposite sides of said beams. The chain 273 pivotally supports a plurality, here two, of article-supporting brackets 281, which may be similar to the hooks 272.

A bracket 326 (FIGS. 4 and 14) is secured to the wall 163 between the front reach of the conveyor 252 and the adjacent, rearward reach of the conveyor 253. The bracket 326 comprises an L-shaped arm 327 having a leg 328 which extends transversely of the adjacent reaches of the conveyors 252 and 253. The leg 329 extends upwardly and about perpendicularly away from the leg 328 to support an article.

The'third conveyor 254 comprises an endless chain 282 supported upon a pair of vertically spaced sprockets 283 and 284. The sprocket 283 is supported upon a shaft 286 which is rotatably supported by a bearing 287 (FIG. 1) secured to the beams 136 and 138, the shaft 286 extending therebetween. The sprocket 284 is supported upon a shaft 288 which is rotatably supported by a bearing (not shown). The shaft 288 further supports a second sprocket 289 (FIG. 4). An endless chain 291 is supported upon he sprocket 289 and the sprocket 292 (illustrated in dotted lines in FIG. 4) which is supported upon a shaft 293 rotatably supported at both ends by bearings (not shown). The shaft 293 extends beneath the portion 222 of shield 221.

The end of the shaft 293 illustrated in FIG, 3 supports a further sprocket 294, and the shaft 288 supports a further sprocket 301. The sprocket 301 and a second sprocket 308 support an endless chain 309. The sprocket 308 is secured to a shaft 310 which is rotatably supported by a bearing (not shown) secured to the beam 126A.

The shaft 293 further supports an air actuated clutch 298 (FIG. 3), which is operated by a solenoid valve which will be discussed hereinbelow in the section entitled ELECTRICAL SYSTEM.

The endless chain 282 (FIG. 4) pivotally supports an arm 297 having a hooked bracket 296 which extends through the plane defined by the frontward reaches of the chains 273 and 273A (FIGS. 4 and 5 The fourth conveyor 255 (FIG. 4) comprises an endless chain 302 supported sprockets 303, 304, 305 and 306. The uppermost sprocket 303 is supported upon a shaft 311 which is rotatably supported by the bearing 248 (FIG. 1) disposed externally of the wall 163. The sprocket 306 is supported upon a shaft 312 which is rotatably supported by a bearing (not shown) secured to the inner surface of the wall 163. The sprocket 305 is supported by a shaft 313 which is rotatably supported by a bearing (not shown) secured on the beam 148. The endless chain 302 is further engaged by a plurality of idler sprockets 307 to adjust the tension in the chain 302.

The lower sprocket 304 (FIG. 4) is supported by a shaft 314 which is rotatably supported by a bearing (not shown) secured to the inner surface of the beam 126. The shaft 314 further supports a second sprocket 316 positioned between the sprocket 304 and the inner surface of the beam 126. An

endless chain 317 is supported by the sprocket 316 and a further sprocket 318, which is supported upon a drive shaft 321 that extends the full width of the machine and is rotatably supported by bearings (not shown) secured to the beams 126 and 126A. An idler sprocket 319 is provided to adjust the tension on the endless chain 317.

A sprocket 336 (FIG. 3), which is secured to the shaft 314, and a sprocket 337, spaced rearwardly from the sprocket 336 and supported for rotation by a shaft 339, are engaged by an endless chain 338. The shaft 321 further supports a sprocket 322 so that the sprockets 318A and 322 are on opposite sides of the beam 126A.

The chain 302 (FIG. 4) pivotally supports a plurality of article-support arms 33] upon which the article hooks 332 are mounted so that they extend through the plane of the forward reach of the chain 282 when the article-support hook 332 is adjacent the sprocket 305.

A guide rail 333 (FIG. 4) extends parallel to the rearward reach of the chain 302 from near the sprocket 303 downwardly past the sprocket 305. The guide rail 333 is secured to the beam 152 and to the sidewall 163 in the postheat oven 23. The guide rail 333 includes a dogleg portion 334 which extends below the beam 152 parallel to the rearward reach of the chain 302.

DRIVE MEANS Three electric motors 341, 342 and 343 (FIGS. 3 and 12), which drive the conveyors 252, 253, 254 and 255, are supported upon a stand 344 (FIG. 12) which is secured to the right side of the machine as viewed from the front thereof. In

edges to the right side of the frame 21 and are secured at their outer edges to a pair of vertical legs 349 and 350.

A geartype speed reducer 352 (FIG. 3) is connected to the output of the motor 341. The output shaft 353 of the reducer 352 drives a sprocket 354 which is connected to the sprocket 271 (FIG. 3) by an endless chain 356.

A speed reducer 357 (FIG. 3) is connected to the output of the motor 342. The output 358 (FIG. 12) is connected by a shaft coupling 359, to a shaft 361 which is supported for rotation by a bearing 362, mounted on the shelf 346, and by a bearing 363 secured to the plate wall 159. The shaft 361 supports a pair of clutches 364 and 366, which in this particular embodiment. are air operated and controlled by solenoid valves.

The clutch 364 is connected between the shaft 361 and a sprocket 367 which, along with sprocket 279 (FIG. 3) and an idler sprocket 368, engages and endless chain 369. The clutch 366 is connected between the shaft 361 and a sprocket 371 which, along with the sprocket 322, engages an endless chain 372. The chain 372 is spaced rightwardly of the wall 159 (FIG.

A speed reducer 373 is connected to the output of the motor 343. The output shaft 374 of the reducer 373 supports a sprocket 376 which, along with the sprocket 294 (FIG. 3), engages an endless chain 377.

An exhaust hood 386 (FIG. 1) having a downwardly facing opening 387 is disposed along the lower outside edge of the wall 162 of the oven structure 161 and is secured to the wall 162. The sides of the hood structure 386 converge upwardly to form a circular cross section. A circular conduit 388 extends upwardly away therefrom to an exhaust vent in the ceiling of the building.

LIMIT SWITCH PLACEMENT ing the various conveyors. Limit switches LS-I and LS-2 (FIG. 3) are placed adjacent the upper reach of the chain 356 near the sprocket 271. A pair of lugs 381 and 382 are secured to the chain 356 and positioned to operate the limit switches LS-ll and LS-2.

Limit switch LS-3 (FIG. 4) is secured to the beam 139 adjacent the rearward reach of the chain 273 and adjacent the sprocket 276. The switch LS-3 is positioned so that it is operated by the article-holding brackets 281 as they pass the switch. Limit switch LS-4 (FIG. 5) is secured to the beam 137A and is positioned adjacent and below the sprocket 276A for operation by the articlesupport brackets 281A.

A safety limit switch L$1l is secured to the beam 139A (FIG. 5) adjacent the rear reach of the chain 273A and the sprocket 276A. Switch LS-Il is positioned so that it is operated by the article-support brackets 281A.

Limit switches LS-S, LS-6 and LS-8 are positioned along the forward reach of the chain 309, as illustrated in FIG. 3. Limit switches LS-S and LS-8 are positioned adjacent the sprocket 301 and are secured to the lower portion of the beam 136A. Limit switch LS6 is positioned adjacent the sprocket 308 and is secured to the outer surface of the beam 126A. A lug 383 is secured to the chain 309 and operates the limit switches L8 5, LS-6 and LS-8 as it passes by them.

Limit switches LS-7 and LS-9 are disposed along the upper reach of the chain 338, as illustrated in FIG. 3. Limit switch LS-7 is disposed above and near the sprocket 337, and limit switch LS9 is disposed above and near the sprocket 336. A lug 384 is secured to the chain 338 and operates the limit switches LS-7 and LS-8.

Limit switch LS-Il) (FIG. 5), which is secured to the beam 136A, is disposed along the forward reach of the chain 282A near the sprocket 284A. LS-It) is positioned with respect to the chain 282A so that it operated by the article-holding bracket 296 on said chain 282A.

AIR JETS A pair of air pipes 395 and 396 (FIG. 4) are secured to and between the beams 136 and 136A. The air pipes 395 and 396 extend across the full width of the machine and have jets aimed at the rear of the machine and into the hood 231. A third jet pipe 397 is secured to the beams 138 and 138A and extends across the full width of the machine within the upper end of the hood 231. The jets on the pipe 397 are aimed frontwardly at the rearward reach of the chain 282.

AUXILIARY ARTICLE-HANDLING DEVICE If desired, the machine 15 may be provided with an auxiliary article-handling device 416 (FIG. 10), which comprises a pair of spaced bearings 417 (only one shown in FIG. 10) which rotatably support a shaft 418 which extends across the full width of the machine along the forward side thereof. A pair of arms 419 are secured to the shaft 418 adjacent the bearings and at the ends of the shaft 418. The outer ends 421 of the arms 419 are U-shaped, and the shaft 418 is rotated by drive means (not shown).

ARTICLE HOLDERS An article holder 389 (FIG. 2) is comprised of a bar 391 which is placed in the forwardmost recess 141) of the bracket (FIG. 4). The articles 10 to be coated are provided with small, integral hooks 393 suspended from rods 392 which are pivotally secured to the bar 391.

ELECTRICAL SYSTEM There are many ways in which the electrical system of the machine 15 may be arranged to carry out the purposes of the invention, and the electrical circuit27 (FIG. 13) shows one way in which the system may be designed. However, the invention is by no means limited thereto. This circuit 27 will be explained hereinbelow in the section entitled OPERA- TION.

OPERATION The operation, which has been indicated somewhat above, will first be summarized and then detailed with reference to the structure appearing in FIGS. 1 through 12 and with respect to the circuit diagram shown in FIG. 13.

SUMMARY OF OPERATION The first conveyor 252 (FIG. 4) of the machine 15 has hooks 272 designed to engage an article holder 389 which supports an article 10 and is mounted upon the bracket 135. The conveyor 252 then carries the holder and article upwardly into a first stopping position 10A supported by the hook 272". The duration of this first stop for a standard wire rod shelf is in the range of 45 to 50 seconds, which gives the operator ample time to place another article on the brackets 135. The conveyor 252 then quickly moves the article 10 through 171 into a first dwell position 108 within the preheat oven 22, where it remains for the same 45 to 50 seconds.

Each article 10 must be quickly transported into the preheat oven 22 so that its entire surface is exposed to the same heat. If the article is not transported quickly into the preheat. oven, then the top of the article will be hotter than the remainder thereof, since the top would be the first part into the oven and the last part out.

The conveyor 252 moves the article 10 (FIG. 4) to the second dwell position 10C in which the article remains for the same 45 to 50 seconds. The article 10 is thereafter transferred to the second conveyor 253 which moves the article to a third dwell position 10D, where it is supported by hook 282 for another 45 to 50 seconds. Then, the article 10 is quickly transported downwardly out of the oven 22 through the opening 172 and onto the article-holding bracket 296 on the conveyor chain 282 of the third conveyor 254. The article requires about seconds in all for its moves between dwells within the oven 22. Therefore, the total time in the preheat oven 22 for a standard, wire rod shelf is approximately 155 to 170 seconds. It is recognized, of course, that this time period may be varied for different sizes and types of articles.

The articles 10 (FIG. 4) are quickly transported from the oven 22 into the powder bin 31 where they are held by the dwell timer 404 for a prcdesignated amount of time. The plastic granules in he bin 31 cling to the hot article 10 when the article is moved upwardly and away from the powder bin 31. In general and within known limits, the thickness'of the layer of powdered plastic material on the article will vary according to the time that the article remains in the fluid bed. A jet of air is blown across each article as it moves upwardly toward the postheat oven 23 so that the excess powder granules on the article will be blown into the hood 231 and sucked into the exhaust duct 236 through the openings 232.

The article 10 is transferred from the third conveyor 254 (FIG. 4) to the fourth conveyor 255, as illustrated in dotted lines in FIG. 7, and carried upwardly through the opening 211 into the oven 23. The article 10 is held in the upper part of oven 23 for a predesignated amount of time, such as 45 to 50 seconds, in dwell position 10E as determined by the timer 398. This time interval could, as a practical matter, vary from 20 to 75 seconds, depending upon the article involved.

At the end of the dwell time in position 1015, the article 10 is moved downwardly through the opening 212 into the quench tank 14 where the article-holding bracket 331 releases the article holder 389 onto the support bar 220 (FIG. 10) so that the article remains submerged in the quench tank 14.

The article holder 389 will come to rest at the lower, frontward end of the bar 220 where said holder 389 is located downwardly directly above the U-shaped portion 421 of the arm 419 of the auxiliary article-handling device. The shaft 418 carrying the arm 419 is rotated clockwise, as viewed in FIG. 10, to the position indicated in dotted lines, whereby the article holder 389 is carried from the bar 220 up to an auxiliary stand 422, illustrated in dotted lines in FIG. 10. The operator may then remove the article 10 from the article holder 389 and, at the same time, break the hooks 393 away from the article 10.

Referring now to the detailed operation of the machine 15, the fluidized bed 18 is rendered operative by causing air to flow through the openings 22 into the bottom section of the bin 32. This air then flows upwardly through the filter elements 55 into the upper unit 76 containing the powdered plastic material. The motor 111 is energized and causes the eccentrics 109 to rotate whereby the shafts 105, hence the screen 89, are reciprocated. The springs 96, 98, 99 and 102 center the screen 89 in the bin 31 and restrict the movement of the screen to a substantially horizontal reciprocation.

The reciprocating screen 89 shakes the lower portion of the powdered plastics to avoid the compacting thereof and the formation of lumps. The air being pumped through the powdered plastics material tends to raise the upper level of the bed so that it can readily receive and cover the articles. Also, reciprocation of the screen 89 tends to circulate the powdered plastics so that the bed will apply a uniform and homogenous coating to the articles dipped therein. Moreover, the agitation maintains a balanced mixture where various types of plastics, additives, coloring and the like are combined in the fluidized bed.

The conveyor system of the machine 15 is started by closing the switch 394 (FIG. 13), which energizes the conductors 396 and 397 hence the motors 342 and 343. The output shafts from their respective speed reducers 357 and 373 are controlled by the air clutches connected thereto. Closing of the switch 394 also energizes the timing relay 398 which causes the contact 398-CI to close and energize the relay coil 399 whereby the contact 399-C1 is closed to energize the motor 3417 The contact 399-C2 is also closed, thereby locking in the relay coil 399 through the normally closed switch LS-1.

The upper reach of chain 356 is caused to move leftwardly, as viewed in FIG. 3, by the motor 341 so that the lug 381 will close the limit switch LSr-2 causing the relay coil 401 to be energized. Energization of the relay coil 401 closes the contact 401-C1 and the contact 401-C2, whereby the solenoid 402 is energized to operate the clutch 364 (FIG. 12) which causes the chain 369 to be driven and thereby drive the second conveyor 253 (FIG. 4). The relay coil 401 will be locked in by the closed contact 401-C1 and the normally closed limit switches LS-3. After the lug 381 moves leftwardly past the limit switches LS-l and LS-2, switch LS-1 returns to its normally closed position and switch LS-2 returns to its normally opened position. At some point in time after the lug 381 has passed the limit switches LS-l and LS-2, and before the lug 382 operates the limit switch LS1, the timing relay 398 times out, thereby opening the contact 398-C1. Since the limit switch LS-l and the contact 399C2 are closed, the relay coil 399 is maintained in its energized state. Thus, both conveyors 252 and 253 are started by activation of the timing relay 398.

When the lug 382 strikes the limit switch LS1, thereby opening same to deenergize the relay coil 399, the article in position 10A will have moved to the position 10B and the article in position 108 will have moved into position 10C. Deenergization of the relay coil 399 will result in the opening of the contact 399-C1 to stop the motor 341.

The timing relay 398 is automatic and is designed to close the contact 398-C1 at predetermined intervals of time. In this particular embodiment, the intervals of time range from 20 to seconds.

When the timer relay 398 "times in again, the relay contact 398-C1 will close thereby energizing the relay coil 399. Thus, the electrical process is repeated until the motor 341 is energized again.

If an article 10 (dotted lines in FIG. 4) is held by an articleholding bracket 272 located above the sprocket 258 in oven 22 when the switch 399 is closed, starting of the motor 341 will move the conveyor 252 so that the article-holding bracket 272 moves downwardly and thereby transfers the article holder 389 to the bracket 326 (FIG. 4). This occurs prior to the time that the article-holding bracket 281 on the conveyor 253 adjacent the sprocket 276 (FIG. 4) reaches the bracket 326. As a result, the article holder 389 will be placed on the bracket 326 before the bracket 281 can move upwardly to pick up the article holder 389 and then carry it around the sprocket 274 into a third dwell position 10D within the preheat oven'22.

If an article 10 has been transferred from the first conveyor 252 to the second conveyor 253, and if the article is in the dwell position 10D (FIG. 4), starting of the conveyor 253 will move the article downwardly and thereby deposit the article holder 389 onto the article-holding bracket 296 secured to the chain 282 of the conveyor 254. Movement of the article-holding bracket 281 around the sprocket 286 will result in operation of limit switch LS-3 by the bracket 281 to stop the conveyor 253.

The third conveyor 254 is actuated when the article-holding bracket 281 (FIG. 4) closes limit switch LS-4, which energizes the relay coil 403 and thereby closes the contact 403-Cl and locks in the relay coil 403 through the nonnally closed limit switch LS-6. The contact 403-C2 will be closed to start a dwell timer 404 as well as to energize the solenoid 406 to operate the clutch 298 and start the third conveyor 254. As a result, the article-holding bracket 296, carrying the article holder 389 and the article 10 will move downwardly (FIG. 4) to dip the article 10 into the powder bin 31.

When the article-holding bracket 296 (FIG. 4) reaches the lowest point of its travel, the dwell timer 404 will momentarily interrupt the drive of the conveyor 254 by interrupting the supply of power to the solenoid 406. As a result, the article 10 is momentarily held in the powder bin 31 until the solenoid 406 is energized again by closing of the dwell timer 404. After the contacts on the dwell timer 404 have closed, the clutch 298 (FIG. 3) is engaged again and the article 10 will be raised 332 (FIG. 7) to move past the hook 296 located in the transfer position.

However, prior to the time when the third conveyor is stopped in the dotted line position of FIG. 7, the fourth conveyor 255 is started when the lug 383, secured to the chain 309 (said chain being driven by the same power that drives the third conveyor 254) closes the limit switch LS5. Closing of the normally open limit switch LS- energizes the relay coil 407 which closes contact 407-C1, thereby locking in the relay coil 407 through the normally closed contact of the limit switch LS9. The contacts 407-C2 are closed, thereby energizing the solenoid 408 to operate the clutch 366 thereby causing the chain 372 to rotate counterclockwise as viewed in FIG. 3 and thereby starting the fourth conveyor 255. Through appropriate gearing, the movement of the chain 302 of the conveyor 255 is relatively slow.

The closed limit switch LS-7 energizes the relay coil 409 which closes the contact 409-C1 thereby locking in the relay coil 409 through the normally closed limit switch LS-8. The contact 409-C2 is also closed, thereby energizing the solenoid 406 controlling the clutch 298 on the shaft 293. Thus, the article bracket 296 on the third conveyor is moved from its dotted line position above the sprocket 283 and then to the position illustrated in FIG. 4 at which time the lug 383 (FIG. 3) on the chain 309 opens the limit switch L&8 and deenergi zes the relay coil 409 which opens the contacts 409-C1 and 409C2, thereby deenergizing the solenoid 406 and opening the clutch 290 mounted on the shaft 293 to stop the third conveyor 254.

As the article-holding bracket 296 was moving upwardly away from the powder bin 31, it closed the normally open limit switch LS-10, thereby energizing the relay coil 411 and a timing relay 413. Energization of the relay coil 411 closes the contact 411-C1 to lock in the relay coil 411 and the timing relay 413. Likewise, contact 411C2 is closed resulting in the energization of the solenoid 412 controlling a valve supplying air to the air jets or pipes 395, 396 and 397 (FIG. 4). The length of time during which the air is supplied to the air jets is controlled by a timer 413.

After a predesignated amount of time the lug 384 (FIG. 3.)

on the chain 338 opens the normally closed limit switch LS-9 so that the relay coil 407 will become deenergized, thus opening the contacts 407-C1 and 407-C2 which will deenergize the solenoid 408 thereby opening the clutch 366 and stopping the fourth conveyor 255.

A safety limit switch LS11 is provided in the event that the article-holding brackets 296 and 296A are not positioned correctly at the time when the article holder 389 moves downwardly to be transferred to the article-holding brackets 296 and 296A. The normally closed safety limit switch LS-ll will he opened by the article holder 389 to deenergize the conductor 396 thereby shutting off all systems.

CIRCULATION OF AIR IN OVENS Hot air from a regulated source, which may be the gas burner 202, is pumped by the fan unit 203 (FIG. 6) through the'heating duct 173 into the preheat oven section 22. Part of the hot air escapes from duct 173 through the slots 176 and The rising hot air in the preheat oven 22 enters the return duct 184 through the openings 183 and the hot air in the postheat oven 23 enters the heat duct 196 through the openings 197. y

' Some of the hot air forced into the ovens escapes by flowing out of the openings 171 and 212 and the chimney 189 in the preheat oven. The air that escapes is replaced by fresh filtered air pumped into the system. The suction side of the fan 203 draws the rest of the hot air from the return duct 196 through the connecting duct 199 and the return duct 174 into the plenum 204 at the top of the heating unit 202 from which it is then mixed, if necessary, with air from the fresh air supply and reheated. Thereafter, the recirculated and heated air is returned to the ovens as described above.

Since control of the heat in the two ovens is essential to the most efficient operation of the machine 15, additional control and/or separate heating units for the two ovens may be desired, and such is contemplated.

In a preferred process involving the machine 15, the wire rod in the shelving being coated is of substantially uniform thickness throughout said'shelves. Thus, the heating will be uniform in penetration of the parts with moderate heat settings. However, where parts of dissimilar masses, or densities or sizes or coefficients of heat absorption and/or dissipation are included in the same article, adjustments may be required. For example, the heat may be more intense for a shorter period of time so that similar penetrations of heat, limited by the smallest part, can be maintained with adequate residual to bond the powdered plastics, but without burning same.

Although a particular preferred embodiment of the invention has been described above in detail for illustrative purposes, it will be recognized that variations or modifications of such disclosure, which lie within the scope of the appended claims, are fully contemplated.

Iclaim:

1. An apparatus for applying to a plurality of articles a coating of plastic material having amelting temperature substantially less than the melting temperature of the article, compris- In I first and second oven means adapted to receive said articles;

fluidized bed means below said oven means; first conveyor means adapted to move said articles sequentially into and out of said first oven means, said first conveyor means including first and second endless chain means having article-engaging means connected thereto at uniform intervals therealong, and support means within said first oven means for receiving said articles from said first chain means and releasing said articles to said second chain means;

second conveyor means adapted to receive said articles from said first conveyor means and move said articles sequentially into and out of said fluidized bed means, said second conveyor means including third endless chain means having engaging means thereon for receiving said articles from said second chain means and for moving said articles into and out of said fluidized bed;

third conveyor means adapted to receive said articles from said second conveyor means and move said articles sequentially into and out of said second oven means, said third conveyor means including fourth endless chain means having engaging means thereon for receiving said articles from said third endless chain means and thereafter moving said articles into and out of said second oven means;

cooling means for reducing the temperature of the coated articles after removal thereof from said second oven means, said cooling means comprising tank means containing a liquid coolant and disposed adjacent said fourth endless chain means whereby said articles are moved by said fourth chain means into said tank;

drive means connected to said conveyor means for causing movement thereof; and

control means for controlling the operation of said drive means and for synchronizing the movement of said conveyor means.

2. An apparatus according to claim 1, wherein said oven means open downwardly and said fluidized bed means and tank means open upwardly;

wherein said first and second chain means both extend from points below said first oven means upwardly into said first oven means; and

wherein said third conveyor means extends from adjacent said tank means upwardly into said second oven means.

3. An apparatus for applying a plastic coating to a plurality of articles, one at a time, wherein said coating has a melting temperature substantially below the melting or decomposition temperature of the article, comprising:

an upright frame structure;

first and second, downwardly opening oven means mounted upon the upper part of said frame structure, and means for heating said oven means;

an upwardly opening receptacle means adapted for a fluidized bed of powdered plastics near the lower end of said frame structure and below the first oven means;

an upwardly opening tank means for holding a liquid coolant near said receptacle means and below the second oven means; first endless conveyor means extending from beneath said first oven means upwardly into said first oven means, said endless conveyor means having article-engaging means attached thereto at predetermined intervals there-along;

article-support means for receiving said articles from said first conveyor means and supporting same within said first oven means;

second endless conveyor means extending from below said first oven means into said first oven means and having articleengaging means attached thereto at predetermined intervals therealong for removing said articles from said support means and moving them downwardly out of said first oven means;

third endless conveyor means extending from near the lower end of said second conveyor means to a point adjacent the open end of said receptacle means and having article-engaging means thereon for receiving said article from said second conveyor means and moving said articles into and out of said receptacle means;

fourth endless conveyor means extending from adjacent said tank means upwardly into said second oven means and closely adjacent said third conveyor means, said fourth conveyor means having article-engaging means thereon for receiving said articles from said third conveyor means and moving them into and out of said second oven means and into said tank means;

drive means for effecting movement of said endless conveyor means; and

control means adapted to operate said drive means and to synchronize the movement of said conveyor means.

4. An apparatus according to claim 3, wherein said control means causes said endless conveyor means to be moved intermittently so that said article-engaging means thereon are advanced through a sequence of dwell positions wherein the articles supported thereby are held for time intervals of predetermined duration.

5. An apparatus according to claim 3 wherein each conveyor means comprises a pair of endless chain means mounted upon opposite sides of said upright frame structure and operated in synchronism by said drive means; and

including article hanger means removably engagcablc by said article-engaging means and adapted to support said articles.

6v An apparatus for applying to a plurality of articles a coating of plastic material having a melting temperature substantially less than the melting temperature of the articles. comprising:

first oven means adapted to receive said articles therein for causing preheating thereof prior to coating of said articles with plastic material;

second oven means disposed adjacent said first oven means for receiving and heating the coated articles;

coating means disposed adjacent said oven means and including a fluidized bed of particulate plastic material for applying a substantially uniform coating of plastic material to said articles;

cooling means disposed adjacent said oven means and defining a cooling zone for permitting rapid cooling of the heated coated articles, said cooling zone containing a cooling fluid for contacting and cooling said articles;

first conveyor means having article-engaging means thereon for sequentially moving said articles into said first oven means for permitting heating of said articles;

second conveyor means having article-engaging means thereon for sequentially moving said articles into and out of said fluidized bed whereby said articles receive a coating of plastic material;

means associated with said first and second conveyor means for permitting the preheated articles to be transferred from said first conveyor means to said second conveyor means;

third conveyor means having article-engaging means thereon for supporting the coated articles within said second oven means and for sequentially moving said coated articles out of said second oven means into said cooling zone, said third conveyor means being separate from said first conveyor means; and

means associated with said second and third conveyor means for permitting the coated articles to be transferred from said second conveyor means to said third conveyor means.

7. An apparatus according to claim 6, wherein said cooling means includes a tank containing a liquid cooling medium therein, article-support means associated with said tank for supporting and immersing the coated articles within the liquid cooling medium, said support means permitting the coated articles to be transferred thereto from said third conveyor means, and handling means disposed adjacent said tank for sequentially removing the coated articles from the tank.

8. An apparatus according to claim 6, wherein said first and second oven means are disposed closely adjacent one another in side-by-side relationship, said first oven means having downwardly directed opening means for permitting articles to be moved upwardly into and downwardly out of the interior thereof, and said second oven means also having downwardly directed opening means for permitting the coated articles to be moved upwardly into and downwardly out of the interior thereof.

9. An apparatus according to claim 8, wherein the fluidized bed is disposed substantially directly under said first oven means whereby said preheated articles are moved substantially vertically downwardly out of said first oven means directly into said bed, and said cooling means including a tank containing a liquid cooling medium therein, said tank being disposed substantially directly under said second oven means for permitting the coated articles to be moved substantially vertically downwardly out of said second oven means directly into said tank.

10. An apparatus according to claim 6, wherein said first, second and third conveyor means respectively include first, second and third endless flexible support means, each said flexible support means having said article-engaging means thereon, drive means interconnected to each said endless support means for causing movement thereof, and control means associated with said drive means for synchronizing the movement of said conveyor means.

11. An apparatus according to claim 10, wherein said control means causes said first, second and third conveyor means to be moved intermittently so that said article-engaging means thereon are advanced through a sequence of dwell positions transporting said articles from said first endless flexible support means to said second endless flexible support means, said fourth support means extending from a position within said first oven means adjacent said first support'means to a position externally of said first oven means substantially adjacent said 18 second support means.

13. An apparatus according to claim 10, wherein said first 4 and third endless flexible support means each have an articletransporting reach disposed within said first and second oven means, respectively, said article-transporting reaches each having a major component of motion in the vertical direction whereby said articles are thus moved vertically a substantial extent while in said first and second oven means. 

2. An apparatus according to claim 1, wherein said oven means open downwardly and said fluidized bed means and tank means open upwardly; wherein said first and second chain means both extend from points below said first oven means upwardly into said first oven means; and wherein said third conveyor means extends from adjacent said tank means upwardly into said second oven means.
 3. An apparatus for applying a plastic coating to a plurality of articles, one at a time, wherein said coating has a melting temperature substantially below the melting or decomposition temperature of the article, comprising: an upright frame structure; first and second, downwardly opening oven means mounted upon the upper part of said frame structure, and means for heating said oven means; an upwardly opening receptacle means adapted for a fluidized bed of powdered plastics near the lower end of said frame structure and below the first oven means; an upwardly opening tank means for holding a liquid coolant near said receptacle means and below the second oven means; first endless conveyor means extending from beneath said first oven means upwardly into said first oven means, said endless conveyor means having article-engaging means attached thereto at predetermined intervals therealong; article-support means for receiving said articles from said first conveyor means and supporting same within said first oven means; second endless conveyor means extending from below said first oven means into said first oven means and having article-engaging means attached thereto at predetermined intervals therealong for removing said articles from said support means and moving them downwardly out of said first oven means; third endless conveyor means extending from near the lower end of said second conveyor means to a point adjacent the open end of said receptacle means and having article-engaging means thereon for receiving said article from said second conveyor means and moving said articles into and out of said receptacle means; fourth endless conveyor means extending from adjacent said tank means upwardly into said second oven means and closely adjacent said third conveyor means, said fourth conveyor means having article-engaging means thereon for receiving said articles from said third conveyor means and moving them into and out of said second oven means and into said tank means; drive means for effecting movement of said endless conveyor means; and control means adapted to operate said drive means and to synchronize the movement of said conveyor means.
 4. An apparatus according to claim 3, wherein said control means causes said endless conveyor means to be moved intermittently so that said article-engaging means thereon are advanced through a sequence of dwell positions wherein the articles supported thereby are held for time intervals of predetermined duration.
 5. An apparatus according to claim 3 wherein each conveyor means comprises a pair of endless chain means mounted upon opposite sides of said upright frame structure and operated in synchronism by said drive means; and including article hanger means removably engageable by said article-engaging means and adapted to support said articles.
 6. An apparatus for applying to a plurality of articles a coating of plastic material having a melting temperature substantially less than the melting temperature of the articles, comprising: first oven means adapted to receive said articles therein for causing preheating thereof prior to coating of said articles with plastic material; second oven means disposed adjacent said first oven means for receiving and heating the coated articles; coating means disposed adjacent said oven means and including a fluidized bed of particulate plastic material for applying a substantially uniform coating of plastic material to said articles; cooling means disposed adjacent said oven means and defining a cooling zone for permitting rapid cooling of the heated coated articles, said cooling zone containing a cooling fluid for contacting and cooling said articles; first conveyor means having article-engaging means thereon for sequentially moving said articles into said first oven means for permitting heating of said articles; second conveyor means having article-engaging means thereon for sequentially moving said articles into and out of said fluidized bed whereby said articles receive a coating of plastic material; means associated with said first and second conveyor means for permitting the preheated articles to be transferred from said first conveyor means to said second conveyor means; third conveyor means having article-engaging means thereon for supporting the coated articles within said second oven means and for sequentially moving said coated articles out of said second oven means into said cooling zone, said third conveyor means being separate from said first conveyor means; and means associated with said second and third conveyor means for permitting the coated articles to be transferred from said second conveyor means to said third conveyor means.
 7. An apparatus according to claim 6, wherein said cooling means includes a tank containing a liquid cooling medium therein, article-support means associated with said tank for supporting and immersing the coated articles within the liquid cooling medium, said support means permitting the coated articles to be transferred thereto from said third conveyor means, and handling means disposed adjacent said tank for sequentially removing the coated articles from the tank.
 8. An apparatus according to claim 6, wherein said first and second oven means are disposed closely adjacent one another in side-By-side relationship, said first oven means having downwardly directed opening means for permitting articles to be moved upwardly into and downwardly out of the interior thereof, and said second oven means also having downwardly directed opening means for permitting the coated articles to be moved upwardly into and downwardly out of the interior thereof.
 9. An apparatus according to claim 8, wherein the fluidized bed is disposed substantially directly under said first oven means whereby said preheated articles are moved substantially vertically downwardly out of said first oven means directly into said bed, and said cooling means including a tank containing a liquid cooling medium therein, said tank being disposed substantially directly under said second oven means for permitting the coated articles to be moved substantially vertically downwardly out of said second oven means directly into said tank.
 10. An apparatus according to claim 6, wherein said first, second and third conveyor means respectively include first, second and third endless flexible support means, each said flexible support means having said article-engaging means thereon, drive means interconnected to each said endless support means for causing movement thereof, and control means associated with said drive means for synchronizing the movement of said conveyor means.
 11. An apparatus according to claim 10, wherein said control means causes said first, second and third conveyor means to be moved intermittently so that said article-engaging means thereon are advanced through a sequence of dwell positions wherein the articles supported thereby are held for time intervals of predetermined duration.
 12. An apparatus according to claim 10, wherein said first conveyor means includes a fourth endless flexible support means having article-engaging means thereon for movably transporting said articles from said first endless flexible support means to said second endless flexible support means, said fourth support means extending from a position within said first oven means adjacent said first support means to a position externally of said first oven means substantially adjacent said second support means.
 13. An apparatus according to claim 10, wherein said first and third endless flexible support means each have an article-transporting reach disposed within said first and second oven means, respectively, said article-transporting reaches each having a major component of motion in the vertical direction whereby said articles are thus moved vertically a substantial extent while in said first and second oven means. 